Any statutory scheme which draws a sharp line between the sexes solely for the purpose of achieving administrative convenience necessarily commands dissimilar treatment for men and women who are similarly situated and therefore involves the very kind of arbitrary legislative choice forbidden by the Constitution.

Sharron Frontiero, a lieutenant in the United States Air Force, applied for housing and medical benefits for her husband, Joseph, whom she claimed as a "dependent." While servicemen could claim their wives as dependents and get benefits for them automatically, servicewomen had to prove that their husbands were dependent on them for more than half their support. Joseph did not qualify under this rule, and therefore could not get benefits. Sharron sued, and the case was appealed up to the Supreme Court. Lt. Frontiero was represented by Joseph J. Levin, Jr., of the Southern Poverty Law Center, who argued the case before the Court on her behalf. Future Justice Ruth Bader Ginsburg, representing the ACLU as amicus curiae, was also permitted by the Court to argue in favor of Frontiero.

A plurality of the Court (JusticesDouglas, White, Marshall and Brennan, who wrote the plurality's opinion) found the military's benefit policy unconstitutional, because there was no reason why military wives needed benefits any more than similarly situated military husbands. The Air Force argued that the policy was intended to save administrative costs by not forcing the military bureaucracy to determine that every wife was in fact a dependent. Justice Brennan dismissed this argument, saying that, although as an empirical matter more wives than husbands are dependent for support on their spouses, still, by automatically granting benefits to wives who might not truly be dependents, the Air Force might actually be losing money because of this policy—and the Air Force had not presented evidence to the contrary.

More importantly, the plurality argued for a strict standard of judicial scrutiny for those laws and regulations that classified on the basis of sex, instead of mere rational basis review. (See the appropriate section of the Equal Protection Clause article for more information on the different levels of Equal Protection scrutiny.) A heightened standard of review, the plurality argued, was needed due to America's "long and unfortunate history of sex discrimination":

[T]he sex characteristic frequently bears no relation to ability to perform or contribute to society. As a result, statutory distinctions between the sexes often have the effect of invidiously relegating the entire class of females to inferior legal status without regard to the actual capabilities of its individual members. [Citations omitted.]

Justices Blackmun and Powell, and Chief JusticeBurger concurred in the result, but, in an opinion written by Justice Powell, declined to decide whether discrimination on the basis of sex should attract strict scrutiny. Justice Powell gave two reasons for leaving this question open. First, that determination was not necessary to decide the case at bar, as the result was "abundantly" supported by the Court's earlier decision in Reed v. Reed. Second, Justice Powell wrote that "deferring" on this question was supported by the ongoing debate about over the Equal Rights Amendment which, if adopted, would resolve the question precisely and "represent the will of the people accomplished in the manner prescribed by the Constitution." Justice Stewart also concurred in the result, but said nothing about the Equal Rights Amendment; instead, he stated only that he agreed that the statutes in question "work an invidious discrimination in violation of the Constitution." Justice Rehnquist dissented. Thus, Frontiero won her case by an 8 to 1 vote.

^Technically, the case was decided under the Fifth Amendment's Due Process Clause, not under the Equal Protection Clause of the Fourteenth Amendment, since the latter applies not to the federal government but to the states. However, because Bolling v. Sharpe, through the doctrine of reverse incorporation, made the standards of the Equal Protection Clause applicable to the federal government, it was for practical purposes an addition not to due process, but rather to equal protection jurisprudence.